FTTH (Fiber to The Home) is a representative example of optical access. In optical access, in general a passive optical communication network in which a terminal station device and a plurality of end-terminal devices are connected is used.
With such a configuration, optical access realizes economical service provision. In the passive optical communication network, communication between the terminal station device and the end-terminal device is multiplexed by means of time-division multiplexing. Communication from the terminal station device to the end-terminal device (hereinafter referred to as “uplink communication”) is realized by using a control protocol called MPCP (Multi-Point Control Protocol) (refer to Non-Patent Document 1). The transmission amount and the transmission start time in the uplink communication of each end-terminal device are centrally controlled in the terminal station device. There has also been proposed a technique for achieving a high band utilization efficiency by determining a transmission amount by using a requested amount from each end-terminal device (refer to Patent Document 1).
In recent years, there has also been proposed a communication system in which another communication network is accommodated via a passive optical communication network.
In this type of communication system, the terminal station device of a passive optical communication network, and a high-order device connected to the high-order of the terminal station device are controlled in cooperation with each other. By performing the control in cooperation with each other, it is possible to reduce delay in uplink communication from the end-terminal device to the terminal station device. There has been proposed a technique for realizing an economical network installation by applying a passive optical communication network to a mobile wireless communication service network (hereinafter referred to as “mobile network”) which has a very strict requirement for a delay (refer to Patent Document 2). Specific examples of mobile networks include LTE (Long Term Evolution) and LTE-advanced. In these types of techniques, the terminal station device performs band allocation to each end-terminal device using wireless resource information notified from the high-order device. At this time, it is necessary to establish clock synchronization between the terminal station device and the high-order device.